Hitherto, when a pressure-sensitive film to be used for a purpose such as decoration is applied to an adherend, air is often trapped between the pressure-sensitive film and the adherend, which has caused a risk of degrading the external appearance of the adherend. In order to avoid the above defect, a good deal of skill is required, and even if this defect can be eliminated by a skill, much labor is required for squeezing the film, so that a long time has been required for the application thereof.
In the pressure-sensitive adhesive sheet material disclosed in Japanese Examined Patent Publication (Kokoku) No. 44-17040 and the position-justifiable pressure-sensitive adhesive tape disclosed in Japanese Unexamined Patent Publication (Kokai) No. 3-181578, concavities are formed in a carrier or carrier web, and non-tacky materials or glass beads are provided in the formed concavities, whereby the pressure-sensitive adhesive is prevented from being in direct contact with the adherend, which results in slidability, and the application becomes easy. However, this pressure-sensitive adhesive sheet material and position-justifiable pressure-sensitive adhesive tape have the problems in that an additional step is required to provide concavities in a carrier or carrier web, that, after a film has been squeezed onto an adherend, the pressure-sensitive adhesive concavities disappear, and the adherend and the pressure-sensitive adhesive cease to be in point contact with each other, so that when air remains in the central part of the film, it becomes unescapable and so forth.
The pressure-sensitive adhesive composition disclosed in Japanese Examined Patent Publication (Kokoku) No. 45-17074 is obtained by mixing light, fragile and thin-walled glass beads with a liquid adhesive composition and applying the obtained mixture onto a sheet and drying it. The thus obtained pressure-sensitive adhesive having convex portions is sufficiently slidable and its application is therefore easy. However, this pressure-sensitive adhesive composition has the problem that, after a film has been squeezed onto an adherend, the pressure-sensitive adhesive convex parts disappear, and the adherend and the pressure-sensitive adhesive cease to be in point contact with each other, so that when air remains in the central part of the film, it becomes unescapable.
The gas permeable pressure-sensitive adhesive member disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2-45582 has the structure that a porous gas-permeable substrate is provided with a gas-permeable pressure-sensitive adhesive layer containing hollow beads, and also with many micropores communicating with the pores in this substrate. Such a structure has the problems in that the kinds of usable substrates are limited because of the porosity of the substrate, that a specific equipment is required in order to partially eliminate the pressure-sensitive adhesive liquid from the side of the gas-permeable substrate by a gas blow method or air suction method after the coating of the pressure-sensitive adhesive, and so forth.
The wrapping adhesive tape disclosed in Japanese Unexamined Utility Model Publication (Kokai) No. 59-763 is intended for preventing the air from being trapped by partially providing an adhesive layer. This adhesive tape has the problem that, since a pressure-sensitive adhesive needs to be scattered by a dot system, a specific coating machine for this purpose is required.
The repeelable pressure-sensitive adhesive sheet disclosed in Japanese Unexamined Patent Publication (Utility Patent) No. 61-168146 is intended for obtaining repeelability by adding a specific amount of elastic microspheres with a specific size into a pressure-sensitive adhesive layer. However, the optimum range of the amount of added elastic microspheres is so wide that the above repeelable pressure-sensitive adhesive sheet cannot substantially be used for the usage of the present invention, requiring permanent adhesion, because of the low adhesive strength. In addition, in the above repeelable pressure-sensitive adhesive sheet, the particle diameter of the elastic microspheres is defined preferably within the range between 1 and 100 .mu.m, so that this adhesive sheet is not suitable for the pressure-sensitive adhesive film which does not trap the air, intended by the present invention. Further, the sheet is not particularly limited, either, so that this repeelable pressure-sensitive adhesive sheet could not be used directly for the pressure-sensitive adhesive film intended by the present invention.